Electrically conductive two component twisted yarn and fabrics for textile flat goods for clean rooms and clean room wearing apparel

ABSTRACT

A fabric according to the invention is made by weaving electrically nonconductive lower ply warp yarns together with electrically nonconductive lower ply filling yarns in a 1/1 plain weave. Within a pattern repeat, 4 electrically nonconductive upper ply filling yarns are additionally interwoven in a plain weave fashion with 4 electrically nonconductive upper ply filling yarns. Two electrically conductive combination yarns, as warp yarns within a pattern repeat, are interwoven with all electrically nonconductive upper ply filling yarns within the pattern repeat into a 2/2 twill weave opposite to the twill woven upper ply warp yarns. The nonconductive filling yarns of the lower ply thus provide an additional supporting effect for the electrically conductive combination yarns. By these means, the electrically conductive combination yarns are stressed substantially less by bending, thus not breaking, whereby the electrical conductivity is thus retained and the functional life is prolonged. The fabrics find use as clean room textile flat goods and in wearing apparel for clean rooms.

This is a division of application Ser. No. 926,596 filed Nov. 3, 1986.

The invention relates to an electrically conductive twisted yarn orthread comprising the combination of a metal wire and an electricallynonconducting synthetic filament component and which, when suitablywoven and finished, is suitable for fitting out "clean rooms", as wellas for clean-room wearing apparel, a method for producing such a yarn,and woven fabric comprised of the aforementioned yarn.

BACKGROUND OF THE INVENTION

It is well known that fabrics and garments for "clean rooms" in theareas of microelectronics, medicine, pharmaceuticals, industrialceramics and the film and sound recording industry are predominantlymade of polyester filaments, which admittedly have an adequately lowparticle emission, but do not guarantee protection of the components,for example, sensitive microcircuits, sensitive integrated circuits andother sensitive semiconductors, against static electricity.

To reduce or eliminate the aforementioned defect, it is furthermoreknown that antistatic chemicals may be applied in the form of additivesin detergents and rinsing aids or in the form of sprays on the wearingapparel. Admittedly, these chemicals reduce the cling effect of thewearing apparel to the body of the wearer, but they do not prevent thebuild-up of a high static charge on the surface of the wearing apparel.Moreover, such chemicals are not washfast.

Aside from a thin, narrow metal foil as a central layer, known metallaminated threads have a covering layer comprising a thin plastic film.For this reason, these threads are not suitable for the purposementioned, since only the thin edges of the middle metal layer areexposed, with which the static electricity cannot be dissipatedadequately.

Admittedly, charges of static electricity are dissipated and dispersedby the use of metal fibers and metal threads in yarns. However, thefabrics manufactured therefrom have a negative effect on the particleemission, due to the hairiness of the yarns, and are therefore notsuitable for "clean rooms".

Moreover, untextured monofilaments have been used, which achieveelectrical conductivity owing to the fact that they have a plurality ofelectrically conductive particles, which are applied on or embedded inthe surface of the monofilaments and thus impart electricalconductivity. These electrically conductive monofilaments are twistedtogether with at least one synthetic filament, which is neither texturednor electrically conductive. The fabric produced from these filamentsand the wearing apparel produced therefrom admittedly are suitable for"clean rooms", since the particle emission is low an the electricalconductivity is good. However, they are susceptible to failure resultingfrom a mutual shift of the individual components when subjected to theaction of mechanical forces. As a result, malfunctions of theconductivity of the fabric may arise due to damage to the conductivecomponent.

SUMMARY OF THE INVENTION

It is an object of the invention to avoid these disadvantages and toprovide an electrically conductive combination twisted yarn, which has aminimal particle emission as well as a minimal particle permeability,dissipates or disperses static electricity and has optimum cleaning andcare properties, as well as good wearing properties.

A further object of the invention is to develop a fabric which, asidefrom safeguarding the property of electrical conductivity, significantlyincreases the loop strength and crack resistance of the wire in thecombination thread, decisively decreases the particle permeability andimproves the wear comfort.

To achieve these objects, the present invention provides, using a metalcomponent, an electrically conductive two component (hereinafter"combination") twisted yarn, which is suitable as a basis for textileflat goods and has the requisite conductivity, the textile characterbeing retained.

Further according to the present invention, an electrically conductivecombination twisted yarn, which uses a metal component, is provided bymeans of a wrapping process operating according to the hollow spindleprinciple process, the yarn being suitable as a basis for textile flatgoods and having the requisite conductivity, the textile character beingretained.

Additionally, the present invention provides a fabric construction, inwhich electrically conductive combination threads are interlaced so thatthe loop strength and crack resistance of the fine wire in thecombination thread are increased substantially.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic plan view of the weave of an upper ply of a fabricincorporating electrically conductive combination threads according tothe invention;

FIG. 2 is a schematic view illustrating pattern design of the weave of afabric incorporating electrically conductive combination threadsaccording to the invention;

FIG. 3 is a schematic cross-section of a fabric according to theinvention in which the arrow points to the fabric face which is theupper ply; and

FIG. 4 is a schematic cross-section of a fabric according to theinvention in which the arrow points to the fabric face which is theupper ply.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electrically conductive combination twisted yarn of the presentinvention comprises a metal wire component and a preferably jet-texturedsynthetic filament component, the electrically conductive component,conducted to the synthetic filament component with an at least 20% lowertension/thread tensile force than is applied to the synthetic filamentcomponent, lying electrically conducting in a helical line on thesurface of the twisted yarn. This combination twisted yarn represents acombination of a synthetic filament yarn with a metal wire, producedwith a yarn tension level of preferably 8% of the denier-relatedbreaking strength of the synthetic filament yarn. The metal componentcomprises a conventional commercial chromium-nickel-molybdenum alloywhich, however, is not in use in the spinning sector.

In a related aspect of the present invention, a polyester filament yarn,having an extremely low elasticity and produced according to the jetprocess, is used as a core component with a metal wire being wrappedaround the core component, the tension being applied to the corecomponent yarn by means of known infinitely variable yarn brakesamounting at most to 12% of the breaking strength of the core componentyarn. The sheath component comprises a metal wire of a knownchromium-nickel-molybdenum alloy which, with an approximately parallelwinding, is on a rotatable creel spool and, by means of a downtwister,is wrapped around the core component in heilcal form, at a spindle speedof 10,500 r.p.m., at the rate of 350 turns/minute.

This combination twisted yarn is used in a fabric repeatedly in the wrapand filling directions, it being characteristic that, aside from thiscombination twisted yarn, a plurality of untextured and/or texturednonconductive synthetic filaments are used in both directions of thefabric.

The weave of the fabric is preferably designed so that the conductivecombination twisted yarn is woven repeatedly in the warp and fillingdirections, so that the conductive component of the combination doubleyarn is situated repeatedly at the surface, so as to achieve goodconductivity for the dissipation of static electricity.

Furthermore, this fabric must have a plurality of thread crossings, inorder to ensure minimal particle emission and particle permeability.Aside from these properties, an appropriate wear comfort is assured bythe use of textured threads. This fabric is dyed and/or finished byknown technologies without significant additional expenditures. Whenmanufacturing garments from the fabrics so woven and finished, it isnecessary that the manufactured parts be so assembled, that as manyconductive combination twisted yarns as possible are in contact.

Textile flat goods in which electrically conductive combination threadsare incorporated can consist of a flat fabric with a 2/1 twill weave inwhich the diagonal lines appearing on the surface of the weave run inthe "Z" direction. For this construction, the electrically conductivecombination yarn is interlaced "rigidly" due to frequent yarn crossings,which stress the electrically conductive combination thread in bendingat very short intervals. With this, the usefulness, for example thelasting effectiveness of the conductivity, can be curtailed. The dangerexists that the fine wire in the combination yarn will break, forexample, as a result of the mechanical stress when the fabric is beingworn on the body. Such breakages would lead to local interruptions ofcontinuous electrical conductivity. The fine wire, due to such abreakage, will become detached from the structural formation and bringabout unsatisfactory wear comfort. Breakage occurs because of the lowloop strength and crack resistance as well as the low elasticity of thefine wire.

Therefore, in accordance with the present invention, an electricallyconductive combination yarn is interlaced flexibly in a multi-plyfabric, preferably a two-ply fabric, the electrically conductivecombination yarns in the upper ply being woven in loosely and the lowerply stabilizing the unstable elastic upper ply. The lower ply isinterwoven with the electrically nonconductive yarns of the upper ply.The electrically nonconductive warp yarns of the lower ply are disposedin the immediate vicinity of the electrically conductive combinationyarns, which lie in the warp direction. More particularly, theelectrically nonconductive lower ply warp threads are interwoven withthe electrically nonconductive lower ply filling (weft) yarns in a 1/1plain weave. Additionally, within a pattern repeat, 4 electricallynonconductive lower ply warp yarns are interwoven with 4 electricallynonconductive upper ply filling yarns in twill weave fashion. Moreover,2 electrically conductive lower ply combination yarns, as warp yarnswithin a pattern repeat, are interwoven with all electricallynonconductive upper ply filling threads in the pattern repeat in a 2/2"Z" direction twill weave opposite to the 2/2 "Z" direction twill wovenupper ply warp threads. The nonconductive filling threads of the lowerply thus have an additional supporting effect for the electricallyconductive combination threads. By these means, the electricallyconductive combination threads are stressed substantially less bybending, the electrical conductivity is retained and the functionallifetime is prolonged.

Thus, in FIG. 1, the upper ply warp yarns are interwoven with the upperply filling yarns in a 2/2 twill weave (represented by the solid blocksquares 1) and the lower ply filling yarns 1 are the filling yarns of a1/1 plain weave. In FIG. 2, the upper ply warp yarns 4 intersect(interweave with) the lower ply filling yarns at 3 (the intersectionsbeing represented by slanted strokes) and the electrically conductivecombination warp yarns are interwoven with the upper ply filling yarnsat intersections 5 (represented by black dots). In FIG. 3, the upper plywarp yarns 13 are interwoven with the upper ply filling yarns 16, theelectrically conductive combination wrap yarns 15 are also interwovenwith the upper ply filling yarns 16, and the lower ply warp yarns 14 areinterwoven with the lower ply filling yarns 17 as well as with the upperply filling yarns 16. In FIG. 4, the upper ply warp yarns 23 areinterwoven with the upper ply filling yarns 26, the electricallyconductive combination warp yarns 25 are interwoven with the upper plyfilling yarns 26, the lower ply warp yarns 24 are interwoven only withthe lower ply filling yarns 27 and the lower ply filling yarns 27' areinterwoven with both the upper ply filling yarns 26 and the lower plyfilling yarns 27.

As a result of this fabric construction, the electrically conductivecombination threads can be stressed at least 25% more.

In addition to the effect described, the particle permeability isreduced substantially by means of this inventive fabric contruction.Moreover, since it is the lower ply which comes into contact with theskin, a substantially better wear comfort effect is additionallyachieved.

All the effects described are washfast.

The invention will be better understood from the following examples:

EXAMPLE 1:

(A) Electrically conductive combination twisted yarn of nominal size 25tex

This yarn consists of 2 components:

(1) a 0.036 mm diameter chromium/nickel/molybdenum metal wire of nominalsize 8 tex,

(2) a white polyester 80 filament yarn stretch-textured by the jetprocess and having a nominal size of 16.7 tex.

The combined yarn is produced as follows:

known doubling-winding process with the process specially controlled asfollows

* tension on metal wire - 80%

* tension on the textured polyester yarn - 100%

* tension force level approx. 8% of the size-related breaking strengthof the polyester yarn.

Use of special grooved drums to make certain that the twisted thread iswound up accurately;

known two-for-one twisting process as winding-doubling feed

* using twisting flyers

* without balloon limiting device

* spindle speed: 9000 r.p.m.

* yarn twisting: 350 r.p.m.

* brake cartridge: 0

* step brake: 1

* thread guide height: 41

* overfeed: 32%

(B) Technical Specifications for the Example 1 fabric for clean-roomuse:

Raw material

* conductive combination twisted yarn of a nominal size 25 tex (asdescribed in A.)

* nonconductive synthetic yarn consisting of polyester 64 filament yarnof nominal size 17 tex together with polyester 32 filament yarn ofnominal size 15 tex

total number of yarns: 7590

warp sequence: 20 yarns of nonconductive synthetic filament (polyester)and 2 yarns of conductive combination double yarn

order of drawing in: straight through

number of frames: 6

reed density: 150/3 (150 reeds, each 10 cm, 3 yarns per reed)

reed width: 168.7 cm

unfinished width: 165 cm

finished width: 152 cm+2 cm

filling sequence: 26 of the nonconductive 15 tex, 32 filament polyesteryarn and 2 of the conductive combination twisted yarns

filling density, raw: 330 threads/10 cm

filling density, finished: 330 threads/10 cm

area related weight, finished: 160 g/m²

weave: 2/1 "Z" direction twill weave

finishing

* washing: known washing process in jigger with addition of oxalic acid

* drying and setting: tentering, drying and setting machine at atemperature of 210° C., residence time of 20-30 seconds

* dyeing: known dyeing process on high-temperature beam at 130° C.

* drying: tentering, drying and setting machine at a temperature of 160°C.

* equalizing on roll.

EXAMPLE 2

Electrically conductive combination twisted yarn of nominal size 25 tex

This yarn consists of the same two components as in Example 1.

The combined yarn is produced as follows:

A twisting process is conducted according to the hollow spindleprinciple. The polyester yarn, textured by the jet process, has a lowelasticity. During the twisting, tension is applied to this corecomponent by means of known, infinitely variable thread brakes up to amaximum corresponding to 12% of the breaking strength of the yarn. Thesheating metal wire is wrapped in a continuous helical line around thiscore component. This metal wire is wound in approximately parallelfashion on a rotating creel spool and is wrapped uniformly at the rateof 350 turns/minute around this core component by a downtwisteroperating at a spindle speed of 10,500 r.p.m.

The combination twisted yarn, so obtained, is woven and finished byknown methods.

EXAMPLE 3:

1. The electrically conductive combination twisted yarn is the same asin Examples 1 and 2.

2. The electrically nonconductive synthetic yarn is the same as in partB of Example 1.

3. The fabric below is constructed using the electrically conductivecombination yarn 1 and the electrically nonconductive yarn 2.

total number of yarns: 8,000

warp sequence: 12 ends of nonconductive yarn and 2 ends of conductivecombination yarn

order of drawing in: broken

number of frames: 12

reed density: 120/4 (120 reeds, each 10 cm, 4 threads per reed)

reed width: 164 cm

raw width: 157.5 cm

finished width: 152 cm±2 cm

filling sequence: even

filling density, raw: 500

filling density,

finished: 510

weave: This is according to the weave configuration shown in FIGS. 1 to3.

FIG. 1 shows the weave of the upper ply, including the electricallyconductive combination yarns

FIG. 2 shows the weave of the lower ply

FIG. 3 shows the point paper design of the weave

Description of the Weave:

    ______________________________________                                        Drawn "solid" black                                                                          The electrically nonconductive -squares in the                                Figures upper ply warp yarns of nominal                                       size 17 tex, 64 filament polyester                                            together with the electrically                                                nonconductive upper ply filling                                               yarns of nominal size 15 tex,                                                 32 filament polyester are woven                                               into a 2/2 "Z" direction twill weave.                          Drawn as black "slashes"                                                                     The electrically conductive lower                              in the Figures ply warp yarns of nominal size                                                17 tex, 64 filament polyester                                                 twisted with the metal wire                                                   together with the electrically                                                nonconductive lower ply filling                                               yarns of polyester filaments                                                  of nominal size 15 tex, 32                                                    filament polyester yarn are woven                                             into a 1/1 plain weave.                                                       Within a pattern repeat, 4                                                    electrically nonconductive lower                                              ply warp yarns are interwoven                                                 with 4 electrically nonconductive                                             upper ply filling yarns in                                                    plain weave fashion.                                           Drawn as black points                                                                        Two electrically conductive                                    in the Figures combination yarns of of                                                       nominal size 25 tex as described                                              in part "1." of this example,                                                 as warp yarns within a pattern                                                repeat, together with all                                                     electrically conductive upper                                                 ply filling threads in the                                                    pattern repeat consisting of                                                  nominal size 15 tex, 32                                                       filament polyester yarns woven                                                into a 2/2 "Z" direction twill                                                weave opposite to the 2/2 "Z"                                                 direction twill weave upper                                                   ply warp yarns.                                                ______________________________________                                    

4. Finishing

* Washing: Known washing process in jigger with addition of oxalic acid

* Drying and setting: Tentering, drying and setting machine at atemperature of 210° C. and a residence time of 20-30 seconds

* Dyeing: known dyeing process on high-temperature beam at 130° C.

* Drying: tentering, drying and setting machine at a temperature of 160°C.

* Equalizing on roll

What we claim is:
 1. Fabric for the production of textile flat goods andwearing apparel for clean rooms comprising electrically conductivecombination yarns and electrically nonconductive synthetic yarns, thefabric having an upper ply of electrically nonconductive combinationyarns and a lower ply stabilizing the upper ply and interwoven with theelectrically nonconductive yarns of the upper ply, wherein the lower plyincludes electrically nonconductive lower ply warp yarns interwoven withelectrically nonconductive lower ply filling yarns into a 1/1 plainweave, 4 electrically nonconductive lower ply warp yarns within apattern repeat additionally interwoven with 4 electrically nonconductivefilling yarns in the upper ply in a plain weave, and 2 electricallyconductive combination warp yarns within a pattern repeat interwovenwith all electrically nonconductive filling yarns in the upper ply in apattern repeat in a 2/2 twill weave opposite 2/2 twill woven upper plywarp yarns.
 2. A fabric as defined in claim 1, wherein the electricallyconductive combination yarns comprise a metal wire and a syntheticfilament component.